In the construction of residential and commercial buildings it is common to have back-to-back bathrooms wherein the hot and cold water supply pipes service shower and tub units on opposite sides of the wall. Prior art shower control valves often have the cold water inlet on one side and the hot water inlet on the other side. As the two supply pipes in the wall are normally side-by-side, it is necessary to provide an awkward cross-over arrangement for one of the shower units. Later inventions provided shower control valve assemblies that utilise a casing having two inlets and a replaceable cartridge unit which can be adjusted in a relatively simple manner at the time of installation so that it is entirely optional as to which of the inlets is connected to the hot water supply pipe and which is connected to the cold water pipe. Commonly assigned Canadian Patent No. 1,050,853 of Mar. 20, 1979 discloses just such an arrangement. The valve assembly of that patent is pressure balanced, with a single handle to control the temperature of the water issuing from the shower. The casing of the patented valve assembly included a single outlet leading to the shower, water for the tub flowing through a separate spout having a diverter valve associated therewith.
The trend in pressure balanced valve assemblies has been towards single handle control valves which are also adapted to control the flow of water to a tub as well as to a shower. U.S. Pat. Nos. 4,681,140; 4,901,750; and 4,905,732 all teach single handle pressure, temperature and/or volume balanced mixing valves.
One of the problems associated with any water flow arrangement is that of water hammer, generated noise which is frequently experienced in pressure sensing mixing valves when they are installed in line with quick closing faucets. Other problems involve cross flow between the hot and cold water supply lines and back flow in either or both of the supply lines.